The invention relates to a motor vehicle including several wheels and a brake system having hydraulically actuatable brakes associated to the wheels, respectively, at least one brake circuit via which the brakes can be actuated, a brake booster via which the brake circuit can be operated, wherein the brake booster can be actuated via a brake pedal actuated by the driver, and at least one pressure generating and/or pressure storage device which is controllable via a control device and via which the hydraulic pressure can be modulated within the braking circuit.
Motor vehicles generally have disk brakes assigned to the respective wheels, wherein drum brakes are sometimes also installed. The brakes are actuated via a hydraulic brake circuit which, in turn, is operated via a brake booster in order to generate the necessary hydraulic pressure. A brake booster is hereby to be understood as including brake pressure generating devices without and with modulation devices, which are used for the provision of ABS and ESC functions. The brake booster, in turn, is coupled in known motor vehicles to the brake pedal, wherein the brake pedal typically is part of a foot lever system on which at least an accelerator pedal or, optionally, a clutch pedal is provided.
Such known braking systems are nowadays designed fail-safe. This means that when a fault occurs in the braking system itself or in a system component such as, for example, corresponding actuating elements, within the communications link to controllers etc., or the energy supply, the braking system is ultimately deactivated. In this context, braking system is understood to be the brake booster and the brake control, usually with the main functions of ABS (anti-lock braking system) and ESC (electronic stability control). This means that these functions are no longer available, sometimes also the brake booster no longer operates normally. The driver thereby serves as a fallback. In case of failure, he assumes the task of braking the motor vehicle by increased force which he introduces via the brake pedal, consequently to build up the required brake pressure. The driver has to stabilize the motor vehicle himself and select a suitable travel mode in order to control and brake it in case of a failure. This means that the driver is included as a fallback in the security concept.
Modern motor vehicles already allow semi-autonomous driving, thus driving in which the driver is at least in part no longer involved in the motor vehicle guidance. Development increasingly is aimed in a direction of relieving the driver as much as possible towards piloted, respectively predominantly autonomous driving. That means that the vehicle including the respective control is automatically capable to guide the motor vehicle longitudinally and transversely without the need for involving the driver. He can attend to other things. With increasing scope of piloted driving, the demands on safety-relevant motor vehicle systems however also increase, which then need no longer be configured “fail-safe”, but “fail-operational”, because they must be able to guide the motor vehicle autonomously, even in the case of a fault, for at least a certain bridging period, that is until the driver himself is actively involved in the driving operation again. This means that the “fail-operational” control must be configured such as if the driver was still actively involved in its entirety. Currently known braking system architectures however, do not allow the realization of such a “fail-operational” behavior since they are still geared to the driver as a fallback.